Production of High-Power Fibers
The transmission of high optical power via fiber optics always poses a challenge. One of the main dangers is cladding modes (undesirable forms of light propagation that spread in the cladding instead of in the core of the fiber).
Especially in high-power systems, they can quickly lead to overheating in the adhesive, connector system, or fiber, and subsequently destroy the fiber. LASER COMPONENTS’ ModeStrip process provides a remedy.
Burning Cladding Modes
In many industrial applications, companies are increasingly relying on fiber-coupled diode laser systems to transmit laser light efficiently and with high beam quality. The welding of sheet metal and plastics, the soldering of electronic components, and the hardening of steel are just a few examples. These devices deliver the desired quality at high power and require very little space. In addition, the laser beam can be flexibly directed to any location with the fiber. The central wavelengths are usually 808 nm or 980 nm. Depending on the fiber cross-section, LASER COMPONENTS supports cw laser power in a range from 35 W to 400 W.
To couple the light, the connection between the laser and the fiber must be manufactured with extreme precision. As a rule of thumb, the beam diameter should not be larger than 80% of the fiber core during coupling: The thinner the fiber, the more complex coupling becomes. At the same time, the divergence angle of the beam must be smaller than the numerical aperture of the fiber. This is especially important when the laser is operated at the upper limits of its power capabilities because then the divergence increases and there is a risk of over-radiating the fiber core.
Light that has not been coupled into the core, but rather into the surrounding cladding, is transmitted in the form of modes known as “cladding modes”. These cladding modes not only cause a loss of performance, but also pose a significant risk of destroying the fiber cable. Since they are not dissipated at the end of the light transmission, they remain “trapped” in the fiber cladding. Their power is released as heat and can cause considerable damage. For example, it is possible for the adhesive of the connector system to heat up or for the fiber to literally burn off, making it unusable afterwards.
Protection through Precision and Technology
To ensure that cladding modes do not cause any damage, several measures are taken when the fibers are assembled. Care is initially taken to ensure that the fiber is positioned as centrally as possible in the connector at both ends to optimally couple the laser beam and prevent cladding modes from occurring. This is particularly important if the beam is not manually adjusted during coupling, as is often the case with larger systems. Although manual alignment is time-consuming, it is usually performed with the highest precision. Assemblies from LASER COMPONENTS are optimally aligned so that they can be easily exchanged according to the plug-and-play principle. Specialized companies such as LASER COMPONENTS achieve centricity values for the alignment of fiber assemblies where the deviation of the fiber center to the ferrule is less than 5 µm. Nevertheless, something can always “go wrong” – especially with unfavorable beam profiles.
The resulting cladding modes can be removed by cladding mode strippers such as the ModeStrip from LASER COMPONENTS. The fibers are processed in such a way that the light is removed from the cladding in a defined manner shortly after coupling. A special fiber processing technique dissipates the laser power in the cladding via the connector's heat sink, preventing thermal damage during decoupling. In addition to laser coupling, mechanical design plays a crucial role in fiber assemblies for industrial applications. In daily operation, the cables are subjected to heavy stress, and mechanical damage to the fiber, such as bending too tightly, can also lead to the development of cladding modes. In movable systems, for example, both a robust connector design and the use of steel reinforcements in the protective sheathing ensure the desired drag chain suitability.
Individual Fiber Solutions
When assembling fiber optic cables, LASER COMPONENTS specializes in custom solutions. For quality assurance, the production area has extensive testing facilities. Upon request, transmission properties, end face quality, centricity, and numerical aperture can be documented. For special requirements, our in-house R&D team develops innovative solutions such as individual coatings for fiber end faces and end caps.
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LASER COMPONENTS Germany GmbH
Product Selection
Optical fibers for laser acupuncture.
FIBRE END FACES WITH ANTI-REFLECTIVE COATING FOR HIGH COUPLING EFFICIENCY.
OPTICAL FIBRES FOR MEDICAL TECHNOLOGY MUST BE MANUFACTURED UNDER ISO13485 CONDITIONS.
Fiber optic data cables for use in the operating room (OR) must be manufactured under cleanroom conditions.
Fiber tips change the radiation characteristics of the fiber. We offer fiber end caps for the input and output coupling of high laser power and spherical lenses, which are used in medical technology.
